Metallurgy

Solidification grain boundary migration (SGBM) occurs in metals and alloys manufactured by casting, welding, or 3D printing, and it affects material properties, but its mechanisms remain largely unknown. Here, the authors show how SGBM can be predicted in various alloys under different conditions.

Strengthening of metals by grain refinement is limited by the inverse Hall-Petch effect. Here, the authors show nanograined metals can be strengthened by exhausting lattice dislocations via triggering of phase transformation at grain boundaries, instead of further grain refinement.

The effect of aliovalent doping on grain boundary is not yet fully understood at the atomic level. Here, the authors report grain boundary structural transformation in α-Al₂O₃ is induced by co-segregation of multiple dopants using atomic-resolution electron microscopy and theoretical calculations.

Dislocation climb is crucial to plasticity and creep of materials. Here, the authors report real-time atomic-scale observations of grain boundary dislocation climb in nanostructured Au at room temperature. The dislocation climb occurs by reconstruction of two atomic columns in the dislocation core.

The phase behavior of grain boundaries can influence the interfacial properties. Here the authors demonstrate nanoscale patterning of a grain boundary by two alternating phases in Cu that exhibit a congruent, diffusionless transition between the two phases.

It is challenging to study how topologically close-packed phases (TCPs) transform between one phase to another. Here the authors use atomic-resolved tools to look at the transformation between μ and P phases, revealing an intrinsic link between seemingly unrelated TCP configurations.

Understanding deformation of Mg along the c-axis is important for wrought processing of Mg. Here the authors report deformation graining in submicron single crystal Mg where the initial single crystal evolves into ultrafine grains that rejuvenates dislocation activities, enabling large plasticity.

Synthetic routes of stabilizing crystal structures can discover atomic pickings with desired properties. Here the authors demonstrate inter-element miscibility of In can act as a stabilizer to create Z3-based ordered alloy without significantly changing the original density of state of Z3-FePd3.

The origins of deformation twins in Mg have remained unclear in the past. Here the authors, by combining in situ experimental observations and atomistic simulations, capture the rapid twinning phenomena in Mg crystals and show that twinning occurs through pure atomic shuffle.

Grain boundary can change its structure upon deformation. Here, the authors show that during this process, grain boundary mobility can be tuned dynamically via a self-stimulated twinning process.

The local variation of grain boundary atomic structure and chemistry caused by segregation of impurities influences the macroscopic properties of polycrystalline materials. Here, the effect of co-segregation of carbon and boron on the depletion of aluminum in a α − Fe grain boundary is shown.

The effect of point defects on mechanical behaviour of materials is generally considered at high temperatures. This work reports a reversible stress-induced migration of point defects during anelastic deformation in CuO nanowires at room temperature resulting from heterogeneous strain distribution.

Electric fields and currents can alter microstructures of materials in unexpected ways. Here the authors report how electrochemical reduction can cause a grain boundary disorder-to-order transition and show the electric field effects on microstructural stability and evolution.

Improving the reversible plastic deformability and damage tolerance of nanosized metals remains challenging. Here, the authors custom-design low angle grain boundaries in metallic bicrystals to achieve controllable plastic reversibility via fully conservative grain boundary migration.

Body-centred cubic metals rarely show twinning during deformation. Here, the authors use high resolution transmission electron microscopy to show tungsten, a body-centred cubic metal, spontaneously undergoes detwinning when unloaded.

Aspects of twinning in hexagonal-close-packed crystals remain elusive. Here, the authors directly image twinning in rhenium nanocrystals and show the process is mediated by disconnections on Prismatic│Basal interfaces as the twin initially deviates from its ideal orientation before it is corrected.

Grain boundaries can improve the radiation resistance of a material by annihilating point defects formed under irradiation, however the atomistic mechanism is still unclear. Here the authors demonstrate grain boundaries absorb point defects through the climb motion of disconnections.

Exactly how seemingly simple solid-state precipitation occurs in alloys remains elusive. Here, the authors show that excess vacancies introduced into a nanoscale, irradiated or deformed aluminium-copper alloy enable template-directed nucleation of the known strengthening phase θʹ.

The deformation mechanisms of micron-sized twinned metals are well-understood, but it is not so for twinned nanocrystalline metals. Here, the authors use high resolution microscopy to image the deformation of nanocrystalline twinned platinum and show that grain boundary behaviors dominate plasticity below 6 nm.

The microstructural evolution during the sliding of two surfaces against each other is complex and remains poorly understood. Here, the authors use electron microscopy to elucidate the different deformation mechanisms occurring at the beginning of sliding.

In metals, dendrite orientation during crystal growth has been hypothesized to be affected by compositional additions. Here, the authors combine molecular dynamics and experiments in the aluminium-samarium system to prove solute atoms can affect dendrite orientation via interfacial energy changes.